I was halfway out of the door, and very pleased to have fixed a computer, when the owner called me back. “Hang on,” she said. “These squarey bits are much too small. They weren’t like that before.” I sighed, put down my backpack and reached for the mouse. This must be what it’s like fixing a broken-down car on a windswept highway, rescuing the family inside from frostbite and certain death, only to be told by the occupants that while the engine now worked, the radio didn’t.

Welcome to the thankless world of Helping Friends With Their Computer Problems. It’s a fool’s errand, take it from me. In the past few weeks I’ve attempted to fix four computers, with a success rate of 25%. Of course none of this is the user’s fault. No one really prepares us for when things go wrong, and while on that one occasion I was able to fix the main problem and those squarey bits, my friend is none the wiser about what to do if it goes wrong again. So here, for one time only, is my Idiot’s Checklist Of Things To Do When Something Goes Wrong With Your Computer. Of course I claim no responsibility for any advice you may follow, and do not lure me over to your place to fix it (unless it’s with an offer of some Battenburg Window Cake, to which I’m rather partial).

1) Try turning the computer off and turning it on again. I know it sounds obvious, but six times out of 10 this fixes it. (If necessary, unplug the power cable, remove the battery if it’s a laptop, and then leave the computer for five minutes first. This drains the memory, as well as allowing you to get yourself a cup of tea.)

2) Assuming your computer now does load as normal, you have either fixed the problem, or you’re having a problem with a specific program or a specific device you’ve plugged into your computer. The trick now is to isolate the problem. In most cases, you’ll get an error message alerting you to the problem — usually a separate window (“this program has performed an illegal operation and will now go to jail” or somesuch). Take note of which program is causing the problem. It’s not always obvious.

3) In my friend’s case, it was Eudora, an e-mail program. Every time she tried to check her mail, it crashed with a message, that while cryptic (“an unhandled error has occurred”) at least informed me who the culprit was. The next trick, then, is to see whether someone else has had the same problem. Assuming you have an Internet connection (if you don’t, call up a friend who does), check the manufacturer’s Web site and go to their Support page. Search for something relevant like “crash” and “check mail.” No point in reinventing the wheel: If someone else has had the same problem as you, chances are it’s recorded somewhere on the Net.

4) In Eudora’s case, they do a great job of listing possible options for fixing your problem, and after trying about eight of them, everything worked. But if this doesn’t happen, you can still try stuff out yourself. For example, try closing all other programs you don’t need, including, if you’re in Windows, all the ones in the system tray (usually by right-clicking the icon and selecting Exit).

5) Still no joy? Run an updated virus check on your whole computer, and sit tight until it’s done. Don’t have a virus checker installed? Shame on you, but try this free on-line one: www.trendmicro.com/en/products/desktop/housecall/. If you have a virus aboard, that may be your problem.

6) No virus? Try reinstalling the program or device in question (make sure you have the original program file or CD-ROM first). To do this, open the Control Panel in the Settings menu, and Add/Remove Programs. Once the program’s uninstalled, reboot your computer and reinstall the program. If it’s a piece of hardware, open the System icon instead of Add/Remove Programs, find the Device Manager tab and right-click on the device that doesn’t work. Select uninstall. Once you’re done, reboot. You may have to now reinstall the drivers that make the device work.

7) Still not working? Try cleaning up the Registry — the place where Windows stores all the settings that make your programs run (or crash, depending on your point of view). Here’s a free program, EasyCleaner, that does a good job of it: www.toniarts.com/ecleane.htm. Once the program has run its course, reboot and try the program again.

8) If it’s still not working, try checking the hard disk for errors (Accessories/System Tools/Scan in Windows; Windows XP won’t have this option). If that’s still not helping, try removing some of the components of the program in question. Eudora, for example, has extras called plug-ins that may be causing the problem. Microsoft Outlook and Word have similar add-ons that are often the culprit. Remove those and you may be okay.

9) Still no luck? I hate to say it, but you may have bigger problems. You could try reinstalling Windows, but before you take that kind of step you may want to try consulting a professional, since you’re entering Scary Territory.

More on reinstalling operating systems in a future column. In the meantime, print this checklist out, stick it above your computer and stock up on Battenburg Cake, in case I’m dumb enough to come round.